The present invention relates to a steering device in a vehicle and particularly to a rack and pinion mechanism used in a steering device.
A rack and pinion mechanism is widely used in a steering device in which steering torque and rotating displacement produced by a steering handle are suitably converted and transmitted to steering wheels through a link mechanism to thereby turn the vehicle. The rack and pinion mechanism includes a pinion rotatively mounted in a housing, a rack constituted by a rack bar portion (hereinafter simply referred to as rack bar) arranged to be linearly movable through the housing and a rack teeth portion (hereinafter simply referred to as rack teeth) formed on the rack bar and operatively coupled with the pinion such that the rotation of the pinion effects linear movement of the rack bar, and a support yoke contacting slidably with the rack bar in the housing. The rack bar is slidably in contact with the support yoke with its under surface being made to be in face-to-face contact with the support yoke, so that the frictional force developed due to sliding contact between the rack bar and the support yoke causes considerable wear in the relevant contact surfaces and thus reduces transmitting efficiency of rack and the pinion mechanism. As the result, feeling of handling becomes deteriorated.
In U.S. Pat. No. 3,421,387 filed by Frederick John Adams and issued Jan. 14, 1969, it is proposed that a roller member such as a ball, a reel, a spool, or the like, is rotatably mounted in a housing and a rack bar is supported at its under surface by the roller member. In this arrangement, the sliding resistance or friction on the support surface of the rack bar in the housing decreases and light handle feeling may be obtained upon steering the handle. However, the transmitting efficiency increases too much in the entire range of handling and it becomes easy to suffer from the influence caused by kickback or vibrations in rectilinearly running of a vehicle, resulting in a disadvantage that the handle may freely rotate so as to deteriorate the handle feeling.